Highly porous catalytic materials with Pd and ionic liquid supported on chitosan

Chitosan was used to immobilize phosphonium‐based ionic liquids, combined with silica particles, to prepare catalytic materials in the form of highly porous monoliths. These catalytic materials were studied for the hydrogenation of 4‐nitroaniline into p‐phenylenediamine in the presence of formic acid as hydrogen donor in a column reactor. Experimental conditions for the elaboration of the materials were evaluated by their impact on palladium sorption, on the structure of the materials, and on their catalytic efficiency. The concentration of chitosan in the initial solution and the size and concentration of silica particles had to be carefully chosen to elaborate homogeneous materials, with good mechanical resistance and stability in water. The chitosan characteristics and the type of ionic liquid immobilized in the material did not significantly affect the structure of the materials but proved to be crucial for their catalytic efficiency. Higher catalytic performances were obtained using materials prepared from chitosan of high‐deacetylation degree and with Cyphos IL‐101. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Poisoning of Pt/C catalysts by CO and its consequences over the kinetics of hydrogen chemisorption

The initial rate of hydrogen dissociation was studied as a function of irreversible CO coverage at 353 K on 30 wt.% Pt/carbon catalysts (Pt/C) prepared according to different processes. The Pt/C catalysts exhibit similar Pt dispersion (D  0.07) and mean Pt particles size (dp  16 nm). The turnover frequency (number of hydrogen molecules dissociated per CO-free surface Pt atom) was determined as a function of CO coverage from 0.0 to 0.8. The evolution of TOF as a function of CO coverage is in agreement with the model of CO adsorbing on low coordination sites (edges, corners) and then spreading across the faces to grow islands as Brandt suggested in the past (R.K. Brandt, M.R. Hughes, L.P. Bourget, K. Truszkowska, R.G. Greenler, Surf. Sci. 286 (1993) 15–25). At high CO coverage (0.8), TOF depends on the process by which the Pt/C catalyst was prepared. In particular, a Pt/C elaborated according to a colloidal process exhibits a low sensitivity to CO poisoning with an increase of TOF by one order of magnitude.     

A fractographic criterion for subcritical crack-growth boundaries in hot-pressed alumina

The percent intergranular fracture (PIF) was measured along radii extending from fracture origins in hot-pressed alumina specimens, fractured at various loading rates and temperatures, and plotted versus estimates of stress intensity factors (K _I) at the various crack lengths. Minima in PIF occur at values ofK _I that are close to the critical stress intensity factors (K _IC) for cleavage on various crystal lattice planes in sapphire. The subcritical crack-growth boundary (K _I=K _IC of the polycrystalline material) occurs near the primary minimum in PIF suggesting that this minimum can be used as a criterion for locating this boundary. In addition, it was noted that the polycrystallineK _IC (4.2 MPa m^1/2) is very close to theK _IC for fracture on {¯1 ¯1 2 6} planes which is 4.3 MPa m^1/2. These observations suggest that critical crack growth begins when increased fracture energy can no longer be absorbed by cleavage on these planes. There is a secondary minimum atK _I>K _IC that appears to be associated with theK _IC necessary for fracture on combinations of planes selected by the fracture as alternatives to the high fracture-toughness basal plane.     

Phase Stability,Magnetic Properties,and Martensitic Transformation of Ni2−xMn1+x+ySn1−y Heusler Alloy with Excess Mn by First-Principles Calculations

The phase stability, magnetic properties, martensitic transformation, and electronic properties of the Ni_2−xMn_1+x+ySn_1−y system with excess Mn have been systematically investigated by the first-principles calculations. Results indicate that the excess Mn atoms will directly occupy the sublattices of Ni (Mn_Ni) or Sn (Mn_Sn). The formation energy (E_f) of the austenite has a relationship with the Mn content: E_f = 135.27(1 + x + y) − 293.01, that is, the phase stability of the austenite decreases gradually with the increase in Mn content. According to the results of the formation energy of austenite, there is an antiparallel arrangement of the magnetic moment between the excess and normal Mn atoms in the Ni_2−xMn_1+x+ySn_1−y (x = 0 or y = 0) system, while the magnetic moment direction of the normal Mn atoms arranges antiparallel to that of Mn_Ni atoms and parallel to that of Mn_Sn atoms in the Ni_2−xMn_1+x+ySn_1−y (x, y ≠ 0) system. The martensitic transformation occurs in some Ni_2−xMn_1+x+ySn_1−y (x, y ≠ 0) alloys with large magnetic moments of ferrimagnetic austenite. Besides, the valence electrons tend to distribute around the Ni or Mn_Ni atoms and mainly bond with the normal Mn atoms. The results of this work can lay a theoretical foundation for further development of the Ni_2−xMn_1+x+ySn_1−y system as the potential ferromagnetic shape memory alloys.     

Effects of ingestion of a green seaweed,Ulva lactuca,upon caecal and colonic mucosas in the germ‐free rat and in the heteroxenic rat harbouring a human bacterial flora

Effect of ingestion of green seaweed, Ulva lactuca, (70 g kg⁻¹) during a 6‐week period on caecal and colonic mucosas was studied in germ‐free (GF) rats and in heteroxenic (HE) rats harbouring a human bacterial flora (GF rats associated with a human flora). The pH and sulphide concentration of the caecal contents, crypt morphometry, mitotic index and mucin types in the caecal and distal colonic mucosas were determined. In the GF caecum, Ulva strongly increased crypt depth and mucin‐containing cells irrespective of the mucin type studied (neutral, acidic or sulphated) compared to the control diet but had no significant effect on mitotic index. The crypt depth and mucin‐containing cells in the caecum were higher in HE than in GF control rats. They were slightly but significantly increased by Ulva. In the distal colon mucosa of GF rats, Ulva decreased crypt depth and cell number as well as sulphomucin‐containing cells. Conversely, in the HE rats, it increased crypt depth and reduced the number of neutral mucin‐containing cells. These results show that Ulva lactuca exerts an intrinsic effect on mucosal morphometry and on mucin biosynthesis in GF rats. No pathological alteration was observed in the mucosas and no significant modification of the mitotic index or sulphide production was observed in HE rats. © 1999 Society of Chemical Industry     

A nation challenged: The impact of foreign threat on America's tolerance for diversity.

Three experiments investigated how perceived foreign threats to the United States can influence Americans' endorsement of assimilation and multiculturalism as models for foreign and domestic intergroup relations. The initial study, conducted during the 6-month anniversary of the September 11, 2001, terrorist attacks (9/11), discovered that a diverse group of Americans preferred assimilation as a foreign policy and multiculturalism as a domestic policy. After reading that foreigners were supporting the dominant global status of the United States, however, Americans in Experiment 2 no longer expressed this preference for assimilation as a model for foreign intergroup relations. Experiment 3 discovered that Americans primed with 9/11 (i.e., a foreign threat) revealed higher levels of national identity than did those primed with the Columbine massacre (i.e., a domestic threat); moreover, level of national identity predicted support for multiculturalism as a domestic policy and assimilation as a foreign policy. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neutron EDM search using crystal techniques

The importance of initiating new search techniques fpr neutron EDM is emphasised in this short paper. Crystal techniques allow to investigate the interaction of neutrons with electric fields of the order of several 109 V cm⁻¹. This gives the possibility to test CP- and T-violations at stronger electric field levels than ever before.     

Thermodynamic calculations offer insight in the stability of materials: the annealing behavior of amorphous Ru-Si-O and Ir-Si-O thin films

Themodynamic calculations are preformed for the ternary systems Ru---Si---O and Ir---Si---O. Their comparison with experimental results on the annealing behavior of amorphous Ru---Si---O and Ir---Si---O films in vacuum and in oxidizing ambients offers convincing insights in the underlying causes of the better stability of amorphous Ir---Si---O than amorphous Ru---Si---O films under exposure to oxygen, and why the opposite is true in vacuum. These results demonstrate that thermodynamic calculations can help in the judicious selection of materials for the microelectronic technology that have to meet desired goals of stability.     

Bridge Maintenance Robotic Arm:Mechanical Technique to Reduce the Nozzle Force of a Sandblastine Rig

1 Introduction Bridges are an essential element intransport systeminfrastructure worldwide and withtheir high construc-tion costs there is significantly large amount of motivation to extend their life spans . Research into prematurebridge failure has identified rust as a pri mary cause ,[1 ,2].and stripping the structure back to clean,untaintedmetal and then applying a paint coating as an effective means of protection.The most effective/efficient methodof large scale paint stripping from metal…     

Operational termination of conditional term rewriting systems

We describe conditional rewriting by means of an inference system and capture termination as the absence of infinite inference: that is, all proof attempts must either successfully terminate, or they must fail in finite time. We call this notion operational termination. Our notion of operational termination is parametric on the inference system. We prove that operational termination of CTRSs is, in fact, equivalent to a very general notion proposed for 3-CTRSs, namely the notion of quasi-decreasingness, which is currently the most general one which is intended to be checked by comparing parts of the CTRS by means of term orderings. Therefore, existing methods for proving quasi-decreasingness of CTRSs immediately apply to prove operational termination of CTRSs.